A conventional bicycle crank 10 is shown in FIG. 1 and generally includes a connection portion 11 through which a connection hole 12 is defined. A large-diameter groove 13 is defined in the inner periphery of the connection hole 12 and opens to the outside of the connection portion 11. The axle 14 has an end with an engaging portion 15 which has a larger diameter so as to be engaged with the groove 13. However, the end that has the engaging portion 15 is exposed to the outside of the connection portion 11 of the crank 10 so that dust, water can easily enter the opening 16 in the end of the axle 14. A cap 17 is then inserted into the opening 16 of the axle 14 to avoid the entry of the dust and water. However, the cap 17 obviously cannot make the crank 10 to be aesthetic as expected. And the cap 17 increases the cost.
FIG. 2 shows another bicycle crank 20 wherein the connection portion 21 has a connection hole 22 which is defined through the connection portion 21, and a flange 23 extends inward from the inner periphery of the connection hole 22. The axle 24 has its end contacting the inside of the flange 23 and a threaded hole 25 is defined in the end of the axle 24. A bolt 26 is threadedly connected to the threaded hole 25 to connect the axle 24 and the crank 20. However, the bolt 26 can be seen from outside of the crank 20. In addition, the threaded hole 25 and the bolt 26 increase the manufacturing cost of crank and the bolt 26 requires extra assembling step.
The present invention intends to provide the connection of a bicycle crank and an axle which is more secured to the crank and does not exposed from outside of the connection portion of the crank.